I have replaced the Tytronics Model SQ003-H B Gas Simmer Controller three times in 6 months at $126 each I would like to repair the cause and not just replace these. The last time that it went out the Cook (my wonderful wife) was operating the Broiler and noticed that the oven control knob got very hot. I took the range apart today and could find nothing wrong. No shorts or grounds were evident. I have pictures of the damaged simmer control unit if you are interested. What fails in the simmer control unit is a large capacitor and a 1/4 watt resistor. The Prime Suspect causing this is the thermostatic control for the oven. My concern is that the wiring connections on it are gummed up with crud.

Also expertappliance.com wants $340 for a new one while http://www.repairclinic.com wants $153, but is it as good as the OEM part. This is a critical issue with the Cook, because we were told when we bought this stove that its oven was calibrated to maintain the oven temp very accurately.

I don't think the oven thermostat is even in the same circuit as the simmer control for the cooktop, in which case it is unlikely that it's the root cause. Greasy connections, however can cause other problems such as leaking current to ground and raising the ground potential of the entire oven. If this is what's happening, then it's conceivable that this is adversely affecting the simmer control. How to check for this? Good question, thanks for asking.

Use your voltmeter to measure the electrical potential difference between the oven chassis (any unpainted surface) and a ground point that is on a different circuit breaker. Do this with the oven turned on. If everything is peachy with your range, you'll read less than 0.2 volts. More than that, and you have a leak to ground somewhere on your range, greasy connections are always suspect.

The OTHER common cause: dirty power. Samurai's 17th Law of Appliance Repair states that, "Raw power is dirty power." Power comes to us on the power lines with surges, spikes, and swells and then we crap it up further with harmonic distortion from computers and other home office equipment like copiers. The whole issue of power quality will increasingly come to the forefront of everyone's attention as we deal with an aging power infrastructure and the additional stress placed on it by the proliferation of home office equipment. You can read an excellent primer on power quality, it's causes, identification, and mitigation, here.